GCSE Geography

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what is a glacier

a body of or mass of ice that moves

abrasion

rocks and rock fragments frozen into the bottom and sides of a glacier erode/wear away the rocks of the valley/land over which it moves

plucking

the tearing away of blocks/chunks of rock from the surface of the valley sides as the glacier moves over them

how are plucking and abrasion interlinked

plucking and abrasion are interlinked because plucking must occur before abrasion as plucking provides rocks for the glacier , and this allows glacial abrasion to occur as rocks in the valley scrape and scour the valley sides and floor

what is a corrie

a circular hollow , high on the a mountianside , surrounded by steep rocky walls except for a rck lip on the open side

how is a corrie formed

A corrie collects in a hillside hollow , as more snow accumulates , it is compressed and the air is squeezed out forming a névé . other time this becomes glacial ice due to the added pressure of accumulation of snow . Erosional processes such as plucking and abrasion deepen the hollow along side with freeze-thaw weathering . even though the ice is trapped in the hollow and unable to move downhill , gravity encourages the ice to move . this is known as rotational slip , it causes material to be plucked off the steep back wall forming crevasses this material is then used for abrasion to futher deepen the hollow . this means that the front of the corrie is less eroded so a lip forms , when enebales the ice to leave the corrie forming a glacier

A named example of a corrie is :

red tarn corrie in helvellyn in the lake district

what is a drumlin

a low rounded hill made of boulder clay . It has a blunt steeper end and a sharp/pointy/tapered end . they tend to form together in groups or swarms .

we think drumlins form when :

a glacier carrying lots of glacial till advances across a lowland area

the higher lowland temperatures cause the glacier to melt but not fully

it deposits some of the glacial till on the ground be manages to keep carrying some of it forwards

however , due to melting the glacier is now so weak so it does not need much to encourage more deposition

any obstacle in the glaciers path (e.g. rock outcrop) is sufficient enough to slow it down and weaken it even more

as the glacier pushes against the obstacle , the pressure causes the ice to melt even more and lots of deposition occurs

this creates the steep stoss slope of the drumlin

the few bits of remaining ice manages to flow around the obstacle , but it is now so weak that it deposits any remaining glacial till

drumlin swarms show the direction the ice was flowing in (the direction of the drumlins long axes)

a named example of a drumlin swarm is

clew bay in Ireland

draw and label a sketch of a drumlin

what is calving and when is it likely to happen

glacier calving is the breaking off chunks of ice into the sea . As glaciers flow towards the sea they often push over uneaven ground which creates cracks and forms crevasses (large , deep cracks) . when the glcaier reaches the sea , the ice breaks off at these crevasses as there is no land to support the weight of the ice . This is how icebergs are created .

defien glacial budget/ mass balance

the overall gain or loss of snow and ice by a glacier each year i.e. the difference between accumulation and ablation

define zone of ablation

an area towards the top of the mountianside , where the amount of snow that falls during the year is greter than the amount that melts . this is where glaciers form and then start to advance down the mountianside

zone of ablation

an area much further down the mountianside where the amount of snow that melts during that year is greater than the amount that falls . this is where glaciers melt and so start retreat back up the mountianside

A ribbon lake is a large, narrow lake occupying a u-shaped valley. They form after a glacier retreats . they form in hollows where abrasion and plucking was more able to erode the rock as the rock was less resitant softer rock than the surrounding hard rock

a named example of a ribbon lake is

Windemere in the lake district

when the ice melts inside a .... it can leave a small .... lake called a .... a named example is ..... ....in the lake district

corrie

circular

tarn

red tarn

an example of a glacial trough is

Nant Ffrancon , Snowdonia

how are hanging valleys formed

Along its journey down the valley a glacier would be joined by tributary glaciers.These smaller tributary glaciers contained much less ice and so were less powerful. They could not erode their valleys as deeply as the main glacier so, where they met, the tributary valley was left “hanging” above the main valley.

an example of a hanging valley is

Oesmite falls in Yosemite valley in Calafornia

what is a pyramidal peak and how do they form

a pyramidal peak is a 3 or more sided slab of rock making a pointy shaped mountian . they are formed by the erosion of corries , the erosional processes forming pyramidal peaks include : abrasion , plucking and rotational slip . At least 3 corries containing glaciers form back to back and erode deeper and deeper in the landscape until just the central bit of the rock is remaining , which sticks up around the remaing land forming a pyramidal peak

a named example of a pyramidal peak is

Helvellyn in the lake district

what are truncates spurs and how are they formed

these are cliff like edges on the valley side . they are formed when rodges of land (spurs) that stick out into the main valley are cut off as the glacier moves past

what is an erratic an how are they formed

they are rocks and boulders carried by the ice and deposited in a totally different area of rock .

an example of an erratic is

Big Rock in Okotoks Alberta

the largest drumlins can be over

1000 metres long

500 metres wide

and 50 metres high

glacial troughs are .... ... valleys with .... ... they start off as a .... river valley but change to a ..... as the galcier erodes the .... and .... by ..... and ..... making it .... and ....

steep sided

flat bottoms

v shaped

u shaped

sides

bottom

plucking

abrasion

wider

deeper

what are striations

deep groves in surface rocks , made by the sharp edges of rock fragments carried in the bottom/sides of glaciers